Air blast circuit breaker



May 12, 1959 H. FORWALD AIR BLAST CIRCUIT BREAKER Filed Dec. 3l. 1956 I N VEN TOR. /Z/cm kon Torn/a .Zd

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Y y 8 7 9 A s (Milla United States, Patent AIR BLAST CIRCUIT BREAKER Haakon Forwald, Lndvika, Sweden, assigner to Allmnna Svenska Elektriska Aktiebolaget, Vasteras, Sweden, a

Swedish corporation Application December 31, 1956, Serial No. 631,792

4 Claims. (Cl. 20D-148) The present invention relates to an air blast circuit breaker for low or medium tension and is showing its superiority to known breakers through its compact design and through the small quantity of insulating material used in it. The breaker is because of its small dimensions very suitable for enclosed switch gears or other switch gears in buildings, where available space is limited. The invention is chiey characterized in that the breaking contacts of the breaking gap of a circuit breaker are enclosed in an air container and carried by bushing insulators inserted in the walls of said containers. At least one of the breaking contacts is movable and shaped as a tube contact entirely passing through a tubular bushing insulator. The inner diameter of this insulator is only slightly greater than the outer diameter of said movable contact. The movable contact is operated by an air operated mechanism arranged at the outer end of the bushing insulator and carried by such insulator.

According to the invention the breaking gaps are enclosed in containers of sheet steel, preferably joined to earth, The bushing insulators are suitably inserted in opposite walls of said containers. The circuit breaker is suitably so designed that only one breaking gap is enclosed in one cylindrical container, and so that a movable contact is arranged in the cover and a stationary contact in the bottom of said container. In three-phase circuit breakers suitably three breaker units are built together, but it is also possible to arrange three breaking gaps in one common container for instance in one cylindrical container, in which the bushing insulators are attached to the curved surface of the container in two rows opposite each other. The circuit breaker may also be so designed that every breaking gap is provided with two contacts movable against each other.

r[he invention is most easily understood by reference to the accompanying drawing showing a sectional View of the circuit breaker. In the drawing a container 1 is suspended on the wall 3 by means of a bracket 2. ln two opposite walls of the container there are openings in which the two bushing insulators 4 and 5 are inserted. The insulator 4 is inserted in the lower opening and is attached to the container by means of the ring shaped member 6. The insulator 4 carries the stationary contact of the breaking gap. This contact consists of a Contact member actuated by a spring 9 and movably arranged in a sleeve shaped member 8 attached to the rod 7 passing through the insulator. The contact member 10 is electrically connected to the sleeve 8 by means of members not shown in the gure. The insulator 5 is inserted in the upper opening of the container 1 by means of the ring shaped member 11 screwed to the container. The movable hollow contact 12 is slidingly fitted in the metallic sleeve 13 passing through the insulator 5. 14 is a sealing ring between the contact and said sleeve. The movable hollow contact 12 is in its upper part provided with openings 15 and is attached to the valve disc 16 joined to the piston 18 by means of the connecting rod 17. The valve housing 19 and the ICC operating cylinder 20 are built together and are arranged entirely outside the insulator 5. The space under the piston 18 in the cylinder Ztl communicates with the atmosphere through the openings 21 and 22. The space above the said piston communicates through the tube 32, the insulator 23 and the tube 33 with the valve 24. 'Through the tube 25 and through the tubes 34 and 25 the valve 24 and the container 1 communicate with a common pressure air source. Through the tube 26 and the valve 24 the space above the piston 18 in the cylinder 20 may be put into communication with the atmosphere. 31 is a spring actuating the piston in the closing direction ofthe movable contact.

In the drawing the breaking gap is closed. In this position the space above the piston 18 in the operating cylinder 20 communicates with the container 1 through the operating valve 24. The pressure acting on the piston 1S is then forcing the movable contact into abutting contact with the contact member 10, which yields until the lower Surface of the valve disc 16 tightingly rests against the annular edge 27 in the valve housing 19. The breaking gap is opened by operating the valve 24 so that the space above the piston 18 communicates with the atmosphere, so that said space is evacuated and the air pressure in the container, which is acting upon the movable contact, moves said contact upwards until the valve disc 16 tightingy rests against the annular edge 28. During the movement of the movable contact 12 the space in the air container communicates with the atmosphere through the channel 29 and the openings 15 in the contact, the valve housing 19 and the openings 3i) and 22. During the opening movement extinguishing air is striking the breaking arc. The breaking gap is closed again by operating the valve 24 so that pressure air is delivered from the container to the space above the piston 18. The force upon the piston will be great enough to move the Contact to its closed position as the area of the piston is considerably larger than the area of the movable contact, which also is exposed to the pressure of the container. To ensure that the valve disc 16 tightingly rests against the edge 27 also when the container is empty the spring 3l. in the cylinder 20 is arranged to act on the piston 13 in the closing direction of the contact 12.

By arranging a long movable contact in a tubular bushing insulator and air operated operating devices entirely outside this insulator, the diameter of the insulator is considerably reduced, so that it is possible to also reduce the Volume of the air container. As the inner diameter of the insulator is Small, the stress in the insulator will be small, when it is exposed to an inner pressure. In addition to this, the movable contact may be guided by a tubular member arranged in the insulator, so that only the said tubular member but not the insulator is exposed to an inner pressure.

in order to show the position of the breaker, the pressure in the tube for example may be indicated in known ways. Suitably the air outlet is provided with a silencer and with a gas cooler. The insulator may as well outside as inside the air container be provided with flanges, which are increasing the creeping distance.

l claim as my invention:

l. An air blast circuit breaker having a breakin-g gap enclosed in a container permanently lled with cornpressed air, and comprising bushing insulators extending through the walls of said air container, contact members extending entirely through said bushing insulators, at least one of the said contact members being of tubular form and being longitudinally movable within its bushing insulator, and said tubular contact member having an external diameter only slightly less than the internal diameter of the insulating bushing through which it extends,

air controlled means for the operation of the said tubular contact, and a housing enclosing said air controlled means and located upon and carried by the outer end of the bushing insulator containing said tubular contact member. 2. An air blast circuit breaker comprising a container permanently filled with compressed air, xed and movable contact members extending through the walls of said container, an insulating bushing surrounding each contact member and supporting it in the wall of the container, air actuated means for moving one of the contact members longitudinally within its enclosing bushing, and a housing carried by and extending beyond the outer end of the bushing enclosing the movable contact, said housing enclosing the actuating mechanism for said movable contact entirely beyond the outer extremity of its enclosing bushing. 3. An air blast circuit breaker according to claim 1 comprising a metallic sleeve interposed between'the exterior of the tubular contact and the interior of the insulating bushing containing such contact.

4. An air blast circuit breaker according to claim l comprising a metallic sleeve connected to the housing enclosing the air operating means, said sleeve serving as a guide for the movable tubular contact and extending through the insulating bushing containing such contact.

References Cited in the file of this patent UNITED STATES PATENTS 2,392,647 CoX` Jan. 8, 1946 2,459,600 Strom- Jan. 18, 1949 2,574,334l Latour Nov. 6, 1951 2,708,700 Thommen May 17, 1955 2,766,348 Forwald Oct. 9, 1956 FOREIGN PATENTS 179,584 Austria Sept. 10, 1954 

